U.S. patent application number 12/370183 was filed with the patent office on 2009-06-18 for filter for a hearing aid and a hearing aid.
This patent application is currently assigned to Widex A/S. Invention is credited to Leif Hojslet Christensen, Kenneth B. Haugshoj, Jorgen Mejner Olsen, Jorn Eiler VESTERGAARD.
Application Number | 20090154747 12/370183 |
Document ID | / |
Family ID | 37499568 |
Filed Date | 2009-06-18 |
United States Patent
Application |
20090154747 |
Kind Code |
A1 |
VESTERGAARD; Jorn Eiler ; et
al. |
June 18, 2009 |
FILTER FOR A HEARING AID AND A HEARING AID
Abstract
A hearing aid (1) comprises a receiver (19), an output port (6),
a conduit (13) for conveying sound to the port and a barrier
element (39) adapted for baffling entry of ear wax and moisture and
for being acoustically transparent. The invention further provides
a barrier element (39) for a hearing aid comprising a slab having
an exterior surface and through openings for transverse
transmission of sound, wherein the exterior surface is
super-hydrophobic.
Inventors: |
VESTERGAARD; Jorn Eiler;
(Helsinge, DK) ; Olsen; Jorgen Mejner; (Hillerod,
DK) ; Christensen; Leif Hojslet; (Roskilde, DK)
; Haugshoj; Kenneth B.; (Taastrup, DK) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
Widex A/S
Varlose
DK
|
Family ID: |
37499568 |
Appl. No.: |
12/370183 |
Filed: |
February 12, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/DK2006/000470 |
Aug 31, 2006 |
|
|
|
12370183 |
|
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Current U.S.
Class: |
381/325 |
Current CPC
Class: |
H04R 25/654
20130101 |
Class at
Publication: |
381/325 |
International
Class: |
H04R 25/00 20060101
H04R025/00 |
Claims
1. A hearing aid comprising a receiver, an output port, a conduit
for conveying sound to the port and a barrier element adapted for
baffling entry of ear wax and moisture and for being acoustically
transparent, wherein the barrier element comprises a slab with an
exterior surface that has been microstructured and surface coated
by molecular vapor deposition with a moisture repellant matter in
such a way as to make the surface super-hydrophobic, and wherein
the barrier element has a number of through-going pores, the
diameter d of each of the pores being smaller than 200 microns.
2. The hearing aid according to claim 1, wherein the barrier
element has a number of through-going pores, the diameter d of each
of the pores being smaller than 100 microns.
3. The hearing aid according to claim 1, wherein the barrier
element is dimensioned so that the acoustic damping across the
element in the relevant frequency range is maximum 3 dB.
4. The hearing aid according to claim 1, wherein the barrier
element is fitted inside the earpiece so as to be non-accessible to
the general user.
5. The hearing aid according to claim 1, comprising an earwax guard
in the port, arranged acoustically downstream of the barrier
element.
6. The hearing aid according to claim 1, comprising an acoustic
filter arranged acoustically upstream of the barrier element.
7. A barrier element for a hearing aid comprising a slab having an
exterior surface and through-going openings for transverse
transmission of sound, wherein the exterior surface has been
microstructured and surface coated by molecular vapor deposition
with a moisture repellant matter in such a way as to make the
surface super-hydrophobic, and wherein the through-going openings
comprises pores each having a diameter d smaller than 200
microns.
8. The barrier element according to claim 7, wherein the
through-going openings comprises pores each having a diameter d
smaller than 100 microns.
9. The barrier element according to claim 7, wherein the exterior
surface has an air content of at least 60%.
10. The barrier element according to claim 7, wherein the barrier
element is dimensioned so that the acoustic damping across the
element in the relevant frequency range is maximum 3 dB.
Description
RELATED APPLICATIONS
[0001] The present application is a continuation-in-part of
application no. PCT/DK2006/000470 filed on Aug. 31, 2006 and
published as WO-A1-2008025355, the contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to hearing aids. The
invention, more specifically, relates to a filter for a hearing
aid.
[0004] ITE hearings aids generally comprise a shell, which
anatomically duplicates the relevant part of the user's ear canal.
A receiver is placed in the shell in communication with an acoustic
outlet port arranged at the proximal end, i.e. the end of the shell
intended to be situated in the ear canal close to the tympanic
membrane. The distal end of the shell, i.e. the opposite end,
intended to be oriented towards the surroundings, is closed by a
faceplate subassembly, connected to the receiver by leads. The
faceplate subassembly incorporates a microphone, electronics, a
battery compartment and a hinged lid. The microphone communicates
with the exterior through a port, which may covered by a grid.
[0005] Whereas an ITE hearing aid may be regarded as an earpiece
integrating all parts of a hearing aid, a BTE hearing aid comprises
a housing adapted for resting over the pinna of the user and an ear
piece adapted for insertion into the ear canal of the user and
serving to convey the desired acoustic output into the ear canal.
The earpiece is connected to the BTE housing by a sound conduit or,
in case it houses the receiver, by electric leads. In either case
it has an output port for conveying the sound output.
[0006] 2. Description of the Related Art
[0007] WO-A1-00/03561 provides an in-the-ear hearing aid wherein
the acoustic outlet port is protected against contamination by
earwax by means of an earwax guard, which is inserted in port. An
elastic hose connects the port to a receiver. The earwax guard
comprises an essentially tubular element with a through-going
cavity and an abutment collar in one end for sealing abutment
against an edge of the hearing aid housing adjacent the port.
[0008] EP-A2-1432285 shows a method for hydrophobic coating of
components for a hearing aid, such as for the battery lid, the
battery compartment, the housing or a switch.
[0009] DE-A1-102004062279 shows an earwax guard for a hearing aid,
which has been provided with an oleophobic or biofilm-inhibiting
coating.
[0010] EP-A2-1458217 shows an acoustic filter of a hearing
instrument, detachably placed nearby or at the opening for the
acoustic output of the instrument. The filtering element is made of
a polymer material, a synthetic, metallic or ceramic material or a
fabric-like material.
[0011] EP-A2-1432285 provides a method for hydrophobic coating of a
hearing aid for the purpose of preventing entry of moisture into
crevices and openings of the housing.
[0012] U.S. Pat. No. 3,354,022 provides a water-repellant surface
having high and low portions with an average distance between high
portions of not more than 1000 microns and an average height of
high portions of at least 0.5 times the average distance between
them; and having an air content of at least 60%. The air content of
the surface is determined by taking an imaginary plane parallel to
the surface passing through the tops of the high portions of the
surface and measuring at this plane the percentage of the total
surface area which is air. The surfaces may be coated with a solid
having a water contact angle of greater than 90 degrees. These
surfaces are highly water repellant.
[0013] WO-A1-0058415 provides a device for the loss-free transport
or emptying of hydrophilic liquids, which device has raised areas
and cavities on the side facing the liquid, the distance between
the raised areas being between 0.1 and 200 microns and the height
of said raised areas between 0.1 and 100 microns, and the raised
areas being hydrophobic.
[0014] With a hearing aid or an ear piece having an output port
inserted into the ear canal of a user there is a risk of earwax or
moisture entering the port. The earwax may slowly accumulate or it
may be driven into the port by the manipulation of inserting the
hearing aid or the ear piece into the ear canal. The result is that
the port clogs and baffles the acoustic output. For preventing this
it is a standard practice to fit the output port with a replaceable
earwax guard. The earwax guard incorporates baffles or a grid for
establishing a barrier against the entry of earwax while permitting
the passage of sound. The earwax guard may not be effective to
entirely prevent the entry of moisture. The earwax may accumulate
on the earwax guard. Once the earwax guard has been clogged, it is
removed and replaced by a new one.
[0015] As far as pertains the microphone port, there may also be a
risk of entry of moisture and earwax, although there may be less
exposure to earwax as the microphone port faces the surroundings
rather than the ear canal. A grid may be provided, although it may
not be effective for protection against the entry of moisture.
[0016] With a hearing aid fitted with an earwax guard adapted for
easy removal, there is the risk that the earwax guard accidentally
is lost, or that the user removes it without inserting a new one,
e.g. if he or she has no replacement available. When using the
hearing aid without the earwax guard there is a risk of earwax
entering deeper into the hose and ultimately into the receiver,
where it may clog the receiver membrane or it may accumulate on the
integral acoustic filter, if present. The same might happen if the
earwax guard was not effective, i.e. if it was open for penetration
of earwax. In either case, the outcome is a costly service
operation, involving disassembly or replacement of the receiver. It
is estimated that a major proportion of service issues with hearing
aids is related to the entry of earwax or moisture into the output
port.
[0017] Providing the receiver with an external acoustic filter
complicates logistics. An acoustic filter normally serves to
correct acoustic artifacts of the receiver. An acoustic filter
works by absorbing acoustic energy, e.g. for dampening resonance
peaks or otherwise shaping the frequency response. The acoustic
filter must be tailored to the particular receiver in order to
provide a satisfactory shaping with minimal loss of acoustic
energy.
[0018] For logistic reasons it would be easier if a standard earwax
guard could be used for all types of hearing aids. However, a
standard earwax guard necessarily must be acoustically transparent
in order not to absorb energy and possibly distort the desired
acoustic output in a non-controlled way. The requirement for the
filter being acoustically transparent runs against the
consideration of the filter providing an effective barrier against
earwax and moisture. Therefore general earwax guards may not be
effective for preventing the entry of moisture.
SUMMARY OF THE INVENTION
[0019] The invention, in a first aspect, provides a hearing aid
comprising a receiver, an output port, a conduit for conveying
sound to the port and a barrier element adapted for baffling entry
of ear wax and moisture and for being acoustically transparent,
wherein the barrier element comprises a slab with an exterior
surface that has been microstructured and surface coated by
molecular vapor deposition with a moisture repellant matter in such
a way as to make the surface super-hydrophobic, and wherein the
barrier element has a number of through-going pores, the diameter d
of each of the pores being smaller than 200 microns.
[0020] This provides a hearing aid with a barrier element that
combines superior barrier properties against the entry of earwax
and moisture with superior acoustic properties. The barrier element
may be integrated into the earwax guard or it can be arranged in
series with the earwax guard to provide an extra line of
defense.
[0021] The barrier element comprises a slab with an exterior
surface, the exterior surface being surface coated by molecular
vapor deposition with a moisture repellant matter. Suitable matters
are silanes such as perfluoroalkylsilanes or alkylsilanes. The
silanes are chemically attached to the surface by reaction between
hydroxy groups on the silane and on the surface, forming a self
assembled monolayer (SAM).
[0022] Applicants have discovered that microstructuring of the
exterior surface enhances the water repellant properties. The term
exterior surface is here used to designate a surface intended for
generally facing the environment exterior to the hearing aid, as
opposed to a surface intended to face inner parts of the hearing
aid.
[0023] According to an embodiment, the barrier element has a number
of through-going pores, the diameter d of each of the pores being
smaller than 100 microns. In the context of circular openings the
diameter is well known. In case of pores with non-circular cross
sections the diameter designates the largest lateral dimension.
[0024] The pores provide openings for conveying the sound. The
small size of the pores prevents the passage of fluids.
[0025] According to an embodiment, the barrier element is fitted
inside the earpiece so as to be inaccessible to the general user.
This eliminates the risk of the barrier element getting lost, and
thereby protects the more costly internal parts.
[0026] According to an embodiment, the earwax guard in the port is
arranged acoustically downstream of the barrier element. This
places the earwax guard first in line to collect earwax, which is
advantageous as it is the easy part to replace.
[0027] According to an embodiment, the acoustic filter is arranged
acoustically upstream of the barrier element. Hereby the barrier
element does not interfere with the intended function of the
acoustic filter.
[0028] Further advantageous features appear from the dependent
claims.
[0029] The invention, in a second aspect, provides a barrier
element for a hearing aid comprising a slab having an exterior
surface and through-going openings for transverse transmission of
sound, wherein the exterior surface has been microstructured and
surface coated by molecular vapor deposition with a moisture
repellant matter in such a way as to make the surface
super-hydrophobic, and wherein the through-going openings comprises
pores each having a diameter d smaller than 200 microns.
[0030] Within the present context, surfaces exhibiting a contact
angle to water exceeding 120.degree. are termed super-hydrophobic.
Suitable surfaces may be produced by selecting appropriate
materials and providing a micro-surface structure with a high air
content. Still other objects of the present invention will become
apparent to those skilled in the art from the following description
wherein the invention will be explained in greater detail.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] By way of example, there is shown and described a preferred
embodiment of this invention. As will be realized, the invention is
capable of other different embodiments, and its several details are
capable of modification in various, obvious aspects all without
departing from the invention. Accordingly, the drawings and
descriptions will be regarded as illustrative in nature and not as
restrictive. In the drawings:
[0032] FIG. 1 shows a hearing aid;
[0033] FIG. 2 shows a section through part of the hearing aid
including the output port and a barrier element according to a
first embodiment of the invention;
[0034] FIG. 3 shows a section through part of the hearing aid
including the sound output port and two barrier elements according
to a first and a second embodiment of the invention;
[0035] FIG. 4 shows a section through part of the hearing aid
including the sound inlet port;
[0036] FIG. 5 shows a section of a droplet on a surface exhibiting
a small contact angle;
[0037] FIG. 6 shows a section of a droplet on a surface exhibiting
a large contact angle;
[0038] FIG. 7 shows a plan view of the barrier element according to
an embodiment of the invention; and
[0039] FIG. 8 shows a section in a barrier element according to
another embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0040] Reference is first made to FIG. 1, which illustrates a
hearing aid 1 generally comprising a shell 2, a faceplate 3, a lid
5, a sound inlet port 6 and a sound output port 7. The hearing aid
1 is adapted to be positioned in the auditory canal of a user with
the sound output port 7 facing the user's tympanic membrane.
[0041] Reference is now made to FIG. 2 and FIG. 3 for exemplifying
the placement and use of a barrier element according to the
invention.
[0042] FIG. 2 illustrates the sound output segment of the hearing
aid comprising a receiver body 19, leads 22 for electrical
connection, a receiver stub 20, housing an acoustic filter 21, and
a tube or hose 13, which connects the receiver stub 20 with an
aperture in the shell 2, that defines the sound output port 7.
Inserted in the hose 13 is a barrier element according to a first
embodiment of the invention, in the form of an earwax guard 8 which
comprises a cylindrical body 9 having a through-going bore 10 which
is partially closed at one end by an earwax retaining strainer 11.
At the opposite end the cylindrical body 9 is provided with a
round-going collar 44, which in the inserted position abuts against
an end wall part of the shell 2. The earwax guard 8 is frictionally
engaged with tube 13 by an annular bead 38 on the cylindrical body
9 and is thereby held in position during use of the hearing aid
1.
[0043] When a quantity of earwax has accumulated in the earwax
guard 8 to significantly reduce the sound output from the receiver,
the user removes the earwax guard 8 using an applicator (not shown)
and replaces it with a new earwax guard. Further details of the
earwax guard and the applicator can be obtained from
WO-A1-00/03561.
[0044] FIG. 3 illustrates the sound output segment of hearing aid 1
including a barrier element according to a second embodiment of the
invention in the form of a protection cap 14, which is mounted in
the receiver stub 20 or in the hose 13. The protection cap 14
comprises a receiver protection strainer 39 in a supporting ring
40. The protection cap 14 serves as an additional barrier to
protect the receiver from wax or sweat that for some reason enters
the tube 13. This may for example happen if the earwax guard 8
falls out of the sound output port 7 during use of the hearing aid
1. Further, the presence of the protection cap 14 is advantageous
in a situation where the user is out of earwax guards but still
wants to use the hearing aid, or in case the user simply forgets to
insert an earwax guard. The protection cap 14 will thus minimize
the risk of receiver malfunction as a consequence of intruding
earwax and sweat.
[0045] Contrary to the replaceable earwax guard 8, the protection
cap 14 is an internal component of the hearing aid and is thus
inaccessible to the user.
[0046] FIG. 4 shows a sub-assembly of hearing aid 1, mainly
consisting of an electronics module 4, a microphone adaptor 41 and
the lid 5. The microphone adaptor 41 comprises the sound inlet port
6, partially covered by a microphone grid 26, a sound inlet conduit
25, a microphone stub 24, a gasket 43, a microphone port 45, and a
microphone 23. The microphone adaptor 41 further includes a barrier
element according to a third embodiment of the invention in the
form of a microphone protection strainer 42, which is positioned in
the vicinity of the microphone 23. In FIG. 4 the microphone
protection strainer 42 is positioned just outside the microphone
stub 24.
[0047] The strainer 11, the receiver protection strainer 39, and
the microphone protection strainer 42 have surfaces which are
modified to exhibit improved barrier properties towards aqueous and
oily substances, as will be explained in greater detail below. The
primary function of the barrier elements is to protect the receiver
19 and the microphone 23 from potentially damaging intrusion of for
example earwax, water or sweat.
[0048] In the present context improved barrier properties towards
aqueous and oily substances means an improved ability of the
barrier element surface to repel such substances. Generally, the
ability of a solid surface to repel a liquid substance can be
determined in terms of wetting.
[0049] One quantitative measure of the wetting of a solid by a
liquid is the contact angle, which is defined geometrically as the
internal angle formed by a liquid at the three-phase boundary where
the liquid, gas and solid intersect. This is illustrated in FIG. 5,
where .theta..sub.n denotes the contact angle of a water droplet on
a normal untreated surface and in FIG. 6, where .theta..sub.m
denotes the contact angle of a water droplet on a modified
surface.
[0050] Contact angle values below 90.degree. indicate that the
liquid spreads out over the solid surface in which case the liquid
is said to wet the solid. If the contact angle is greater than
90.degree. the liquid instead tends to form droplets on the solid
surface and is said to exhibit a non-wetting behavior.
[0051] In this terminology it follows that the larger the contact
angle, the better the ability of a surface to repel a specific
substance. As indicated in FIG. 5, for untreated surfaces the
contact angle is normally less than 90.degree.. It is well known in
the art to coat a solid with a hydrophobic layer in order to
increase the contact angle and thereby obtain a moisture repellent
surface. Such a surface coating may typically increase the contact
angle of water to around 115-120.degree..
[0052] Applicants have discovered that a structural modification of
the surface of certain materials will improve the ability of the
material to repel aqueous and oily substances. The inventors have
further discovered that the combination of structural modification
and coating significantly improves barrier properties of the
surface. FIG. 6 shows a water droplet on a surface, which has been
modified according to the invention. The increased contact angle
substantially exceeds 90.degree.. In fact, as documented below,
when the surface is modified by a combination of a structuring and
a coating, the contact angle of water exceeds 145.degree. for a
variety of materials. The obtained surface characteristics may be
termed super-hydrophobic. In addition to the super-hydrophobic
surface characteristics, the modified materials obtained
super-oleophobic surface characteristics, as will also become clear
in the following.
[0053] The barrier element surface modification will now be
described in more detail beginning with the surface
structuring.
[0054] The surface structuring is preferably realized on lateral
scales that are much larger than characteristic sizes for atoms and
molecules as well as for grains or other sub-nanometer structures.
The upper limit for the lateral scale will typically be in the
order of 10 microns or larger. The aspect ratio is typically about
1:1 or larger.
[0055] The applied structure can be periodic, quasi-periodic or
random within a certain spatial bandwidth.
[0056] The spatial bandwidth is defined as the range of reciprocal
wavenumbers of the lateral scales of the structure, the wavenumber
being defined as the reciprocal value of the lateral wavelength of
a periodic structure. The structure is applied to at least a part
of the barrier element surface.
[0057] The surface structuring may be performed by a number of
methods, for example by laser processing of the surface with
thermal or non-thermal interactions. Non-limiting examples of
lasers that can be used for surface structuring are CO.sub.2
lasers, solid state lasers, such as Nd:YAG, picosecond lasers and
femtosecond lasers.
[0058] Processes used in the fabrication of micro/nano-electronics
or micro/nano-electromechanical systems as well as other etching or
electrochemical processes can also be applied.
[0059] Reference is made to FIG. 7 for an example of a laser
structured barrier element surface according to the invention, as
seen through a microscope.
[0060] The coating may be applied using a gas phase nano-coating
process. The process is based on applying a hydrophobic coating to
a surface using silanes such as perfluoroalkylsilanes or
alkylsilanes. The silanes are chemically attached to the surface by
reaction between hydroxy groups on the silane and on the surface,
forming a self-assembled monolayer.
[0061] Firstly, the material to be coated is rendered active by
treatment with a plasma, e.g. an oxygen plasma. The plasma
treatment both acts as a cleaning of the surface and as a way of
making the surface reactive by the introduction of hydroxy groups
into the surface.
[0062] Preferably, an adhesion layer that further enhances the
reactivity of the surface by creating even more hydroxy groups may
then be deposited and preferably, a catalyst is added to promote
deposition of the adhesion layer. This step is necessary for
non-metallic substrates and also for glasses and some metals in
order to create stable coatings.
[0063] In the last step, a silane is then reacted with the
activated surface with or without adhesion layer. Preferably, a
catalyst is added to promote deposition of the silane.
[0064] Both silane and adhesion layer are preferably deposited
using a vapor phase reaction scheme. Preferably, the equipment is
so designed as to have a reaction chamber and separate reservoirs
containing the different chemistries used (silane, adhesion layer
precursor and a catalyst) and a remote plasma source. From each
reservoir, well-defined amounts of the different chemistries are
evaporated into a vaporization chamber, from where the vapor is
injected into the reaction chamber once a specified pressure in the
vaporization chamber has been reached. The connections between each
reservoir and the vaporization chamber and between the vaporization
chamber and the reaction chamber are controlled by valves. The
reservoirs and the transfer lines may be heated if necessary in
order to promote vaporization and to avoid condensation in the
transfer lines. Also, the reaction chamber may be heated.
[0065] The system is initially pumped so as to keep a low pressure
in the reaction chamber, transfer lines and vaporization chamber.
Thereafter, the pumping action is halted and the compounds in the
reservoirs are allowed to evaporate into the vaporization chamber.
Once the pre-set pressure in the vaporization chamber has been
reached the vapor is injected into the reaction chamber by action
of the pressure difference between the vaporization chamber and the
reaction chamber. Once a reaction step is completed the reaction
chamber, transfer lines and vaporization chamber are pumped down,
after which a new reaction cycle can start.
[0066] Other gas phase deposition schemes may be used, but the
setup described above has the advantage that plasma activation,
deposition of adhesion layer and deposition of the silane are
carried out in the same equipment in an automated fashion,
providing no need for user intervention between the individual
steps. Furthermore, the precise control over the injected amounts
of chemical substances into the reaction chamber and the control
over the total pressure in the reaction chamber are advantageous in
order to obtain a good quality of the coating both with respect to
structure and surface binding.
[0067] Alternatively, after plasma activation the process may be
performed in liquid solution with the same deposition steps as
previously described. The gas phase deposition is, however, the
preferred technique, as the liquid phase deposition is more
cumbersome and demands several rinse steps.
[0068] Also, polymerization of the silane in the liquid phase
produces by-products that may only be deposited onto the surface
via physical adsorption and not chemical binding, resulting in both
low-quality coatings and in irreproducible coating thicknesses.
[0069] The structuring and/or coating can be applied to the entire
barrier element surface or it can be applied to a part of it. A
controlled structuring of at least a part of the surface in the
immediate vicinity of the pores is particularly advantageous.
[0070] Reference is made to FIG. 8 for an illustration of a barrier
15 having an exterior surface 16, which is structured and coated
according to an embodiment of the invention. The surface is
characterized by a square-wave like profile having alternating
peaks 28 and troughs 29 which can be described in terms of peak
height 32, peak width 30 and trough width 31. A part of the surface
is further provided with a coating 33.
[0071] The barrier performance has been tested for different
materials with different surface structures. A hexagonal pattern of
columns on polytetrafluoroethylene (Teflon.RTM.) was produced with
a femtosecond laser. The column width at the bottom was
approximately 40 microns and the spacing about 40 microns. Each
column had a microstructure generated by the ablation process,
which is non-thermal. This ensures that surface tension does not
smooth the surface locally. Typical fill factors are below 50%. The
fill factor is defined as the ratio of the amount of material left
relative to the amount of material that is removed from the surface
layer. The average laser power was 100 mW, the pulse repetition
rate was 6 kHz, the optical wavelength was 775 nm, and the pulse
width was 150 fs. An increase in contact angle from about 115
degrees to about 150 degrees was observed after the processing,
which included the coating.
[0072] Equivalent experiments were performed with polyethylene
(Stamylex.RTM., available from DEXPlastomers v.o.f, Heerlen, The
Netherlands). The average laser power was 50 mW. An even more
dramatic change in contact angle was observed. Experiments on
stainless steel have also been performed with equivalent results.
The average laser power was in this case 275 mW. Experiments on
steel with random structures generated in conjunction with the
formation of pores of a diameter of 80 microns have produced
similar results.
[0073] Contact angles obtained for water and olive oil on different
surfaces are displayed in the below tables. Olive oil can be
regarded as a representative of liquid earwax.
[0074] The clean surfaces have undergone oxygen plasma treatment
for 10 minutes. The structured surfaces were created by a
femtosecond laser with a wavelength of 775 nm and obtained peak
heights of 25 microns. The surfaces were coated by molecular vapor
deposition.
TABLE-US-00001 TABLE 1 Contact angles for water Clean Structured
Coated Structured and Substrate surface (.degree.) surface
(.degree.) surface (.degree.) coated surface (.degree.) Steel 85
.+-. 5 55 .+-. 5 115 .+-. 5 155 .+-. 5 Glass 40 .+-. 5 10 .+-. 5
115 .+-. 5 150 .+-. 5 Polyimide 70 .+-. 5 <15 115 .+-. 5 160
.+-. 5 PET 80 .+-. 5 125 .+-. 5 115 .+-. 5 150 .+-. 5 PE (Stamylex)
90 .+-. 5 125 .+-. 5 115 .+-. 5 160 .+-. 5 FEP (Teflon .RTM.- 120
.+-. 5 155 .+-. 5 115 .+-. 5 160 .+-. 5 like)
TABLE-US-00002 TABLE 2 Contact angles for olive oil Cleaned
Structured Coated Structured and Substrate surface (.degree.)
surface (.degree.) surface (.degree.) coated surface (.degree.)
Steel -- -- 80 .+-. 5 105 .+-. 5 PE (Stamylex) -- -- 80 .+-. 5 130
.+-. 5
[0075] The large relative increase in the contact angles for both
water and olive oil indicates that the modified surfaces of the
different materials have become super-hydrophobic as well as
super-oleophobic.
[0076] The surface modifications described may be applied to a
traditional earwax guard or filter element, for example by
embossing the material in the filter area with a pre-defined
profile. Preferably, however, a perforated metal or polymer foil,
which is structurally modified and coated according to the above,
is incorporated in a supporting frame to obtain a barrier element
according to the invention with improved hydrophobic and oleophobic
characteristics. This can be done, for example, by casting the
perforated foil in the supporting frame. Alternatively, laser
welding, gluing, or other suitable processes may be applied to
incorporate the perforated foil.
[0077] In order for the barrier element to meet the requirement of
being acoustically transparent, it must be dimensioned so that the
acoustic damping across the strainer in the relevant frequency
range is maximum 3 dB. An example of such a barrier element is
found in WO-A1-00/03561.
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